Tool sharpeners, such as grinders, are used to sharpen cutting edges on wood carving tools, such as cabinet maker tools, chisels, gouges, and the like, and cutting tools, such as plane blades, jointer blades, axes, scissors, knives, and the like. Typically, wet sharpeners have a rotating abrasive grinding wheel mounted along the side of a motor housing where the rim of the grinding stone is kept wet by having it rotate through a tray holding water. The water provides a slight level of lubrication between the tool being sharpened and the rim of the grinding stone to prevent overheating and damaging the tool being sharpened (e.g., burning the tool edge, removing the temper or causing a loss in hardness of the metal tool being sharpened), as well as to decrease the wear of the grinding stone. Some wet sharpeners provide a second grinding, honing or polishing wheel mounted on the opposite side of the housing as the first grinding stone. In view of the multiple uses for such tool sharpeners, the term sharpening as used herein will generally refer to all uses of such tool sharpeners including, but not limited to, grinding, sharpening, honing, polishing, etc.
The sharpener typically has many accessories such as jigs or support tools used to hold carving and cutting tools on a support bar in front of the grinding stone in order to keep the tool steady when it is placed against the grinding stone. A number of small separate gauges also are used to configure the jigs for a desired grinding angle or to measure cutting edge sizes on the tools. Since these numerous accessories are separate from the sharpener and its supports, they can often be lost or misplaced rather easily. Thus, a convenient storage compartment or space is desired to address this problem.
The grinding stone mounted on the side of the motor housing is typically rotated at a single, low speed in order to maintain a certain amount of moisture on the grinding stone rim. However, protracted use causes a reduction of the diameter of the wet grinding wheel and, accordingly, decreases the outer rim or surface speed of the grinding wheel. For example, a 10″ diameter wheel worn down to a 6″ diameter, results in a 40% reduction in surface speed. Erosion of the wet grinding wheel reduces the ability of the grinding wheel to efficiently cut and sharpen a tool (i.e., reduces “cutting aggression”). A wet sharpener is needed that can compensate for this erosion.
Known dry wheel bench grinders, employ a variable speed motor for careful sharpening of fine edges to vary the aggressiveness of the grinding. However, such grinders operate at speeds that are too high to be used with wet sharpeners, such as for example ranges of 2000 RPM and faster. Speeds this high cannot be used on wet sharpeners because at such a high speed, the water is thrown off of the grinding stone and does not adhere to the rim of the grinding stone. Without sufficient water on its rim, the grinding wheel will undesirably wear and overheat. Therefore, it is desirable to address these shortcomings as well as those associated with grinding wheel erosion discussed above.
Conventional wet sharpeners further employ a pendulum structure where the motor hangs from a bar and is free to swing relative to the grinding stone rim. Gravity holds the motor, and more specifically the motor's drive shaft, against the drive wheel of the grinding stone. This enables the motor to rotate the grinding stone purely through friction between its rotating drive shaft and the grinding stone drive wheel.
The gravity-friction based drive force, however, is not always adequate to rotate the grinding stone at a constant speed (constant RPM) or to rotate the grinding stone fast enough. In addition, other factors such as contaminates or liquids on the contact points between the drive wheel rim and drive shaft can further reduce the friction coefficient of the contact. Thus, a need exists for a wet sharpener that provides a stronger frictional force than a simple pendulum-gravity configuration and that can compensate for debris or liquids that reduce friction at the contact points.
The typical, rotating grinding stone is mounted on the side of a sharpener's motor housing and is held near a horizontally extending, support bar also mounted on the motor housing. The support bar supports different jigs which, in turn, support the tool while being sharpened by the grinding stone. The jigs hold the tool at selected angles relative to the grinding stone as the tool is placed in contact with the abrasive, outer rim of the grinding stone.
One such jig is a straight edge jig. This jig includes a base plate that mounts on the sharpener support bar while the tool to be sharpened, such as a flat, hand plane iron, is placed across the base plate of the jig. An upper plate is placed over the tool, to clamp the tool between the base and upper plate. The straight edge jig can be rotated away and toward the grinding stone (i.e., rotated about the horizontal support bar so that the axis of rotation of the jig is parallel to the axis of rotation of the grinding stone). The jig is rotated to select the angle of the tool relative to the grinding stone surface, as well as moved side-to-side along the support bar in front of the grinding stone to sharpen or form a straight cutting edge on the tool.
Another jig is disclosed by U.S. Pat. No. 6,447,384. This jig holds a tool in a casing that can be swiveled horizontally to a range of inclined positions relative to the base of the jig, the support bar and the grinding stone. The jig also can be rotated vertically upon the support bar in a range of grinding angles relative to the grinding stone.
While these jigs enable sharpening or creation of a curved cutting edge, which is horizontal or inclined, they do not enable creation of a true ‘vertical’ cambered surface or cutting edge where the side edges of a flat plate or iron cutting tool are thinner than at the center of the cutting tool. In addition, the jig disclosed by the '384 patent is particularly suited to hold round or beveled tools in its V-shaped seats. While it can hold flat tools, the user tends to have a difficult time arranging the flat tool or iron to sit level within the V-shaped seat of the jig.
U.S. Pat. No. 6,393,712 discloses a multi-jointed arm jig with an elbow joint and wrist joint for sharpening or forming curved surfaces on round tools, such as cylindrical gouges, held at the end of the arm. These jigs, however, do not hold flat tools or irons.
Currently, the only way to create a cambered edge on a flat tool held by these jigs is to manually twist the tool as it is placed along the thickness of the grinding stone. Thus, no way exists to obtain identical cuts from tool-to-tool since the cuts are made by hand.
A need exists for a camber jig that provides support for a flat tool, such as a hand plane iron, while easily forming a cambered cutting edge on the tool without the need for manually twisting or turning the tool by hand. A need also exists to make a repeatable process to produce the same camber on multiple tools.
In addition to jigs, gauges are often used with tool sharpeners in order to recreate the conditions for forming a particularly shaped cutting edge on a tool and for determining the exact angles created on tools. Some gauges are provided for measuring the grinding angle (i.e., the angle of the tool held in a jig or on a tool support relative to the tangent line where the tool meets the circular grinding surface on a grinding stone).
U.S. Pat. No. 6,189,225 discloses a grinding angle gauge that can be used on grinding stones or wheels of varying diameters. The angle gauge includes two adjustable pointers on opposite ends of a frame. At one end, a rounded end of a pointer rests on the grinding stone and can be turned to delineations of the diameter of the wheel. The pointer at the other end of the frame has a flat end for placement on a tool support, jig, or tool at the point where the implement contacts the grinding stone. The pointed end of the second pointer will indicate the angle of the support or jig. One shortcoming with such gauges, however, is that they are often difficult to operate and cost more due to their complex construction. Thus, a less expensive, less complicated gauge is desired for measuring this angle.
Other known gauges are used for measuring the diameter of the grinding wheel or the angle of the cutting edge on the tool. These known gauges, however, are frequently cumbersome to use, inaccurate and cannot be conveniently stored on the sharpener. Thus, a need also exists for gauges that address these shortcomings.